U.S. patent number 6,421,564 [Application Number 09/439,565] was granted by the patent office on 2002-07-16 for bi-chamber cardiac pacing system employing unipolar left heart chamber lead in combination with bipolar right chamber lead.
This patent grant is currently assigned to Medtronic, Inc.. Invention is credited to Brian A. Blow, Jean E. Hudson, Charles A. Yerich.
United States Patent |
6,421,564 |
Yerich , et al. |
July 16, 2002 |
Bi-chamber cardiac pacing system employing unipolar left heart
chamber lead in combination with bipolar right chamber lead
Abstract
In a bi-ventricular pacing system, an implantable pulse
generator optionally having an IPG indifferent electrode is coupled
to a small diameter, unipolar, left ventricular (LV) lead and a
bipolar right ventricular (RV) lead. The LV lead is advanced
through the superior vena cava, the right atrium, the ostium of the
coronary sinus (CS), the CS, and into a coronary vein descending
from the CS to locate the LV active pace/sense electrode at a
desired LV pace/sense site. An LV lead placed on an epicardial
surface can substitute. The RV lead in a preferred embodiment is
advanced into the RV chamber to locate RV active and indifferent
pace/sense electrodes therein. Sensing of RV spontaneous cardiac
depolarizations to provide a RV sense event signal and delivery of
RV pacing pulses is conducted across the RV active pace/sense
electrode and one of the RV or IPG indifferent pace/sense
electrodes. Sensing of LV spontaneous cardiac depolarizations to
provide a LV sense event signal is conducted across the LV active
pace/sense electrode and one of the RV active or indifferent
pace/sense electrodes or the IPG indifferent pace/sense electrodes.
Delivery of LV pacing pulses is conducted across the LV active
pace/sense electrode and the RV indifferent pace/sense electrode. A
similar arrangement is disclosed for left atrial (LA) and right
atrial (RA) pacing and sensing.
Inventors: |
Yerich; Charles A. (Shoreview,
MN), Hudson; Jean E. (Coon Rapids, MN), Blow; Brian
A. (Maple Grove, MN) |
Assignee: |
Medtronic, Inc. (Minneapolis,
MN)
|
Family
ID: |
23745215 |
Appl.
No.: |
09/439,565 |
Filed: |
November 12, 1999 |
Current U.S.
Class: |
607/9 |
Current CPC
Class: |
A61N
1/3622 (20130101); A61N 1/3627 (20130101) |
Current International
Class: |
A61N
1/362 (20060101); A61N 001/18 () |
Field of
Search: |
;600/374,509
;607/4,9 |
References Cited
[Referenced By]
U.S. Patent Documents
Foreign Patent Documents
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196 15 159 |
|
Oct 1997 |
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DE |
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WO 99/29368 |
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Jun 1999 |
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WO |
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Other References
Daubert et al., "Permanent Left Ventricular Pacing With Transvenous
Leads Inserted Into The Coronary Veins", PACE (vol. 21, Part II,
pp. 239-245, Jan. 1998). .
Cazeau et al., "Four Chamber Pacing in Dilated Cardiomyopathy",
PACE (vol. 17, Part II, pp. 1974-1979, Nov. 1994). .
Daubert et al., "Renewal of Permanent Left Atrial Pacing via the
Coronary Sinus", PACE (vol. 15, Part II, NASPE Abstract 255, p.
572, Apr. 1992). .
Daubert et al., "Permanent Dual Atrium Pacing in Major Intra-atrial
Conduction Blocks: A Four Years Experience", PACE (vol. 16, Part
II, NASPE Abstract 141, p. 885, Apr. 1993)..
|
Primary Examiner: Jastrzab; Jeffrey R.
Assistant Examiner: Oropeza; Frances P.
Attorney, Agent or Firm: Wolde-Michael; Girma
Parent Case Text
This patent application claims the benefit of U.S. Provisional
Application No. 60/114090 filed Dec. 29, 1998 and No. 60/145860
filed Jul. 28, 1999.
Claims
What is claimed is:
1. A method of sensing of spontaneous cardiac depolarizations in
right and left heart chambers and delivering right or left heart
chamber pacing pulse to the right or left heart chamber for
improving the hemodynamic efficiency of a sick heart suffering from
conduction delays in conducting depolarizations wherein said method
comprises the steps of: advancing a unipolar pace/sense lead into a
left heart chamber blood vessel to situate a left heart chamber
active pace/sense electrode of the unipolar pace/sense lead
adjacent to the left heart chamber; advancing a bipolar pace/sense
lead into the right heart chamber to locate a right heart chamber
active pace/sense electrode and indifferent pace/sense electrode in
relation to the right heart chamber; sensing right heart chamber
spontaneous cardiac depolarizations across the right heart chamber
active and indifferent pace/sense electrodes and providing a right
heart chamber sense event signal; timing out a pacing interval from
a right heart chamber sense event signal or a previously delivered
pacing pulse; and upon providing of a right heart chamber sense
event signal or upon timing out said pacing escape interval,
selectively generating and delivering one of a right heart chamber
pacing pulse across said right heart chamber active and indifferent
pace/sense electrodes and a left heart chamber pacing pulse along a
trans-ventricular pacing path between said left heart chamber
active pace/sense electrode and said right heart chamber
indifferent pace/sense electrode.
2. The method of claim 1, further comprising the step of: sensing
spontaneous cardiac depolarizations across the right heart chamber
and left heart chamber active pace/sense electrodes and providing a
left heart chamber sense event signal; and the timing step further
comprises the step of: timing out said pacing interval from a right
or left heart chamber sense event signal; and upon a left heart
chamber sense event signal, selectively delivering one of a right
heart chamber pacing pulse across said right heart chamber active
and indifferent pace/sense electrodes and a left heart chamber
pacing pulse across said left heart chamber active pace/sense
electrode and said right heart chamber indifferent pace/sense
electrodes.
3. The method of claim 2, further comprising the steps of: timing
out a triggered pacing delay from the providing of a right heart
chamber sense event signal or a left heart chamber sense event
signal or the timing out of the pacing interval; and at the
time-out of the triggered pacing delay: selectively generating and
delivering the left heart chamber pacing pulse across said left
heart chamber active pace/sense electrode and said right heart
chamber indifferent pace/sense electrodes when said right heart
chamber pacing pulse is delivered across said right heart chamber
active and indifferent pace/sense electrodes at the start of the
triggered pacing delay; and selectively generating and delivering
the right heart chamber pacing pulse across said right heart
chamber active pace/sense and indifferent electrodes when said left
heart chamber pacing pulse is delivered across said left heart
chamber active pace/sense electrode and said indifferent right
heart chamber pace/sense electrode at the start of the triggered
pacing delay.
4. The method of claim 3, wherein the right heart chamber comprises
the right atrium and the left heart chamber comprises the left
atrium.
5. The method of claim 3, wherein the right heart chamber comprises
the right ventricle and the left heart chamber comprises the left
ventricle.
6. The method of claim 1, wherein the right heart chamber comprises
the right atrium and the left heart chamber comprises the left
atrium.
7. The method of claim 1, wherein the right heart chamber comprises
the right ventricle and the left heart chamber comprises the left
ventricle.
8. In an implantable medical device having a pacemaker for sensing
spontaneous cardiac depolarizations in right and left heart
chambers and delivering right or left heart chamber pacing pulse to
the right or left heart chamber for improving the hemodynamic
efficiency of a sick heart suffering from conduction delays in
conducting depolarizations, apparatus comprising: a unipolar
pace/sense lead adapted to situate a left heart chamber active
pace/sense electrode of the unipolar pace/sense lead adjacent to
the left heart chamber; a bipolar pace/sense lead adapted to
situate a right heart chamber active pace/sense electrode and
indifferent pace/sense electrode in relation to the right heart
chamber; and a pacing pulse generator comprising: right heart
chamber sensing means for sensing right heart chamber spontaneous
cardiac depolarizations across the right heart chamber active and
indifferent pace/sense electrodes and providing a right heart
chamber sense event signal; escape interval timing means for timing
out a pacing escape interval establishing a pacing rate from a
right heart chamber sense event signal; pacing pulse generating
means operable upon providing of a right heart chamber sense event
signal or upon timing out said pacing escape interval for
selectively generating and delivering one of a right heart chamber
pacing pulse across said right heart chamber active and indifferent
pace/sense electrodes and a left heart chamber pacing pulse along a
trans-ventricular pacing path between said left heart chamber
active pace/sense electrode and said right heart chamber
indifferent pace/sense electrodes.
9. The pacemaker of claim 8, further comprising: left heart chamber
sensing means for sensing spontaneous cardiac depolarizations
across the right heart chamber and left heart chamber active
pace/sense electrodes and providing a left heart chamber sense
event signal; and wherein: said escape interval timing means
further comprises means for timing out said pacing interval from a
right or left heart chamber sense event signal; and said pacing
pulse generating means is operable upon provision of a left heart
chamber sense event signal for selectively delivering one of a
right heart chamber pacing pulse across said right heart chamber
active and indifferent pace/sense electrodes and a left heart
chamber pacing pulse across said left heart chamber active
pace/sense electrode and said right heart chamber indifferent
pace/sense electrodes.
10. The pacemaker of claim 9, wherein said pulse generating means
further comprises triggered pacing delay timing means for timing
out a triggered pacing delay from the providing of a right heart
chamber sense event signal or a left heart chamber sense event
signal or the timing out of the pacing interval; and wherein: said
pulse generating means is operable at the time out of the triggered
pacing delay to selectively generate and deliver the left heart
chamber pacing pulse across said left heart chamber active
pace/sense electrode and said right heart chamber indifferent
pace/sense electrodes when said right heart chamber pacing pulse is
delivered across said right heart chamber active and indifferent
pace/sense electrodes at the start of the triggered pacing delay
and to selectively generate and deliver the right heart chamber
pacing pulse across said right heart chamber active pace/sense and
indifferent electrodes when said left heart chamber pacing pulse is
delivered across said left heart chamber active pace/sense
electrode and said indifferent right heart chamber pace/sense
electrode at the start of the triggered pacing delay.
11. The pacemaker of claim 10, wherein the right heart chamber
comprises the right atrium and the left heart chamber comprises the
left atrium.
12. The pacemaker of claim 10, wherein the right heart chamber
comprises the right ventricle and the left heart chamber comprises
the left ventricle.
13. The pacemaker of claim 8, wherein the right heart chamber
comprises the right atrium and the left heart chamber comprises the
left atrium.
14. The pacemaker of claim 8, wherein the right heart chamber
comprises the right ventricle and the left heart chamber comprises
the left ventricle.
15. A method of sensing of spontaneous cardiac depolarizations in
right and left ventricles and delivering right or left ventricular
pacing pulse to the right or left ventricle for improving the
hemodynamic efficiency of a sick heart suffering from conduction
delays in conducting spontaneous or evoked depolarizations through
the right and left ventricles that compromise cardiac output,
wherein said method comprises the steps of: advancing a unipolar
pace/sense lead having only a left ventricular active pace/sense
electrode through the coronary sinus of the heart and into a left
ventricular blood vessel branching therefrom to situate the left
ventricular active pace/sense electrode of the unipolar pace/sense
lead adjacent to the left ventricle; advancing a bipolar pace/sense
lead into the right ventricle to locate a right ventricular active
pace/sense electrode in the right ventricular apex and an
indifferent pace/sense electrode within the right ventricular
chamber; sensing right ventricular spontaneous cardiac
depolarizations across the right ventricular active and indifferent
pace/sense electrodes and providing a right ventricular sense event
signal; timing out a pacing escape interval from a right
ventricular sense event signal; selectively generating and
delivering a right ventricular pacing pulse across said right
ventricular active and indifferent pace/sense electrodes at the
time-out of said pacing escape interval; and selectively generating
and delivering a left ventricular pacing pulse along a
transventricular pacing path between said left ventricular active
pace/sense electrode and said right ventricular indifferent
pace/sense electrodes at the time-out of said pacing escape
interval.
16. The method of claim 15, further comprising the step of: sensing
spontaneous cardiac depolarizations across the right ventricular
and left ventricular active pace/sense electrodes and providing a
left ventricular sense event signal; and the timing step further
comprises the step of: timing out a pacing escape interval
establishing a pacing rate from a right or left ventricular sense
event signal.
17. A pacemaker for improving the hemodynamic efficiency of a sick
heart suffering from conduction delays in conducting spontaneous or
evoked depolarizations originating in one of the right or left
heart chamber to the other of the left or right heart chamber
comprising: right heart lead means for locating active and
indifferent right heart chamber pace/sense electrodes in relation
with the right heart chamber; left heart lead means for locating an
active left heart chamber pace/sense electrode in relation with the
left heart chamber; and an implantable pulse generator coupled to
said right and left heart lead means and comprising: right heart
chamber depolarization sensing means coupled with said right heart
chamber lead means for sensing spontaneous cardiac depolarizations
originating in the right heart chamber and conducted cardiac
depolarizations originating in the left heart chamber due to a
spontaneous cardiac depolarization or delivery of a left heart
pacing pulse to the left heart chamber and for providing a right
heart chamber sense event signal in response to either a sensed
spontaneous or conducted cardiac depolarization; left heart chamber
depolarization sensing means coupled with said active left heart
chamber pace/sense electrode and one of said active or indifferent
right heart chamber pace/sense electrodes for sensing spontaneous
cardiac depolarizations originating in the left heart chamber and
conducted cardiac depolarizations originating in the right heart
chamber due to a spontaneous cardiac depolarization or delivery of
a right heart pacing pulse to the right heart chamber and for
providing a left heart chamber sense event signal in response to
either a sensed spontaneous or conducted cardiac depolarization;
right heart pacing pulse output means coupled with said right heart
chamber lead means and selectively responsive to an applied right
heart chamber pace trigger signal for generating and delivering a
right heart pacing pulse across said active and indifferent right
heart chamber pace/sense electrodes to evoke a right heart chamber
depolarization; left heart pacing pulse output means coupled with
said right and left heart chamber lead means and selectively
responsive to an applied left heart chamber pace trigger signal for
generating and delivering a left heart pacing pulse along a
crossventricular pacing path between said active left heart chamber
pace/sense electrode and said indifferent right heart chamber
pace/sense electrode to evoke a left heart chamber depolarization;
and escape interval timing means for timing an escape interval
establishing a pacing rate and providing one or both of the right
and left heart chamber pace trigger signals at the time-out of the
escape interval, the escape interval timing means further
comprising reset means for restarting the timing of the escape
interval upon provision of a pace trigger signal and upon provision
of one of the right or left heart chamber sense event signals that
is not refractory.
18. A pacemaker for improving the hemodynamic efficiency of a sick
heart suffering from conduction delays in conducting spontaneous or
evoked depolarizations originating in one of the right or left
heart chamber to the other of the left or right heart chamber
comprising: right heart lead means for locating active and
indifferent right heart chamber pace/sense electrodes in relation
with the right heart chamber; left heart lead means for locating an
active left heart chamber pace/sense electrode in relation with the
left heart chamber; an implantable pulse generator having a housing
bearing an indifferent housing pace/sense electrode, said
implantable pulse generator further comprising: right heart chamber
depolarization sensing means coupled with said active right heart
chamber pace/sense electrode and one of said indifferent right
heart electrode or housing pace/sense electrodes for sensing
spontaneous cardiac depolarizations originating in the right heart
chamber and conducted cardiac depolarizations originating in the
left heart chamber due to a spontaneous cardiac depolarization or
delivery of a left heart pacing pulse to the left heart chamber and
for providing a right heart chamber sense event signal in response
to either a sensed spontaneous or conducted cardiac depolarization;
left heart chamber depolarization sensing means coupled with said
active left heart chamber pace/sense electrode and one of said
active or indifferent right heart or indifferent housing pace/sense
electrodes for sensing spontaneous cardiac depolarizations
originating in the left heart chamber and conducted cardiac
depolarizations originating in the right heart chamber due to a
spontaneous cardiac depolarization or delivery of a right heart
pacing pulse to the right heart chamber and for providing a left
heart chamber sense event signal in response to either a sensed
spontaneous or conducted cardiac depolarization; right heart pacing
pulse output means coupled with said right heart chamber lead means
and selectively responsive to an applied right heart chamber pace
trigger signal for generating and delivering a right heart pacing
pulse across said active right heart pace/sense electrode and one
of said indifferent right heart or housing pace/sense electrodes to
evoke a right heart chamber depolarization; left heart pacing pulse
output means coupled with said right and left heart chamber lead
means and selectively responsive to an applied left heart chamber
pace trigger signal for generating and delivering a left heart
pacing pulse along a transventricular pacing path between said
active left heart chamber pace/sense electrode and said indifferent
right heart chamber pace/sense electrode to evoke a left heart
chamber depolarization; and escape interval timing means for timing
an escape interval establishing a pacing rate and providing one or
both of the right and left heart chamber pace trigger signals at
the time-out of the escape interval, the escape interval timing
means further comprising reset means for restarting the timing of
the escape interval upon provision of a pace trigger signal and
upon provision of one of the right or left heart chamber sense
event signals that is not refractory.
19. A pacemaker for improving the hemodynamic efficiency of a sick
heart suffering from conduction delays in conducting spontaneous or
evoked depolarizations originating in one of the right or left
heart chamber to the other of the left or right heart chamber
comprising: right heart lead means for locating active and
indifferent right heart chamber pace/sense electrodes in relation
with the right heart chamber; left heart lead means for locating an
active left heart chamber pace/sense electrode in relation with the
left heart chamber; an implantable pulse generator having a housing
bearing an indifferent housing pace/sense electrode, said
implantable pulse generator further comprising: right heart chamber
depolarization sensing means coupled with said active right heart
chamber pace/sense electrode and one of said indifferent right
heart electrode or housing pace/sense electrodes for sensing
spontaneous cardiac depolarizations originating in the right heart
chamber and conducted cardiac depolarizations originating in the
left heart chamber due to a spontaneous cardiac depolarization or
delivery of a left heart pacing pulse to the left heart chamber and
for providing a right heart chamber sense event signal in response
to either a sensed spontaneous or conducted cardiac depolarization;
left heart chamber depolarization sensing means coupled with said
active left heart chamber pace/sense electrode and one of said
active or indifferent right heart chamber pace/sense electrodes for
sensing spontaneous cardiac depolarizations originating in the left
heart chamber and conducted cardiac depolarizations originating in
the right heart chamber due to a spontaneous cardiac depolarization
or delivery of a right heart pacing pulse to the right heart
chamber and for providing a left heart chamber sense event signal
in response to either a sensed spontaneous or conducted cardiac
depolarization; right heart pacing pulse output means coupled with
said right heart chamber lead means and selectively responsive to
an applied right heart chamber pace trigger signal for generating
and delivering a right heart pacing pulse across said active right
heart chamber pace/sense electrode and one of said indifferent
right heart or housing pace/sense electrodes to evoke a right heart
chamber depolarization; left heart pacing pulse output means
coupled with said right and left heart chamber lead means and
selectively responsive to an applied left heart chamber pace
trigger signal for generating and delivering a left heart pacing
pulse along a transventricular pacing path between said active left
heart chamber and said indifferent right heart chamber pace/sense
electrodes to evoke a left heart chamber depolarization; and escape
interval timing means for timing an escape interval establishing a
pacing rate and providing one or both of the right and left heart
chamber pace trigger signals at the time-out of the escape
interval, the escape interval timing means further comprising reset
means for restarting the timing of the escape interval upon
provision of a pace trigger signal and upon provision of one of the
right or left heart chamber sense event signals that is not
refractory.
20. In a multi-site cardiac pacemaker, a method of selectively
sensing spontaneous cardiac depolarizations in the right and left
ventricles and delivering pacing pulses to the right and left heart
ventricles for improving the hemodynamic efficiency of a sick heart
suffering from conduction delays in conducting spontaneous or
evoked depolarizations through the right and left heart chambers
that compromise cardiac output, wherein said method comprises the
steps of: sensing spontaneous atrial depolarizations and providing
atrial sense event signals; timing out an AV delay from the atrial
sense event signals that are characterized as non-refractory;
sensing spontaneous cardiac depolarizations in the right ventricle
and providing right ventricular sense event signals; sensing
spontaneous cardiac depolarizations in the left ventricle and
providing left ventricular sense event signals; timing out a V-A
escape interval establishing a pacing rate from a selected one of
the right and left ventricular sense event signals occurring during
the AV delay or the V-A escape interval that is characterized as
non-refractory; and at the time-out of the AV delay, delivering a
first pacing pulse either as a right ventricular pacing pulse
across said active and indifferent right heart chamber pace/sense
electrodes to the right ventricle to evoke a right ventricular
depolarization or as a left ventricular pacing pulse along a
trans-ventricular pacing path between said active left heart
chamber pace/sense electrode and said indifferent right heart
chamber pace/sense electrode to the left ventricle to evoke a left
ventricular depolarization.
21. In a multi-site cardiac pacemaker, a system for selectively
sensing spontaneous cardiac depolarizations in the right and left
ventricles and delivering pacing pulses to the right and left heart
ventricles for improving the hemodynamic efficiency of a sick heart
suffering from conduction delays in conducting spontaneous or
evoked depolarizations through the right and left heart chambers
that compromise cardiac output, wherein said pacemaker further
comprises: a unipolar left ventricular lead adapted to be advanced
into a left ventricular blood vessel to situate a left ventricular
active pace/sense electrode of the unipolar pace/sense lead
adjacent to the left ventricle; a bipolar right ventricular lead
adapted to be advanced into the right ventricle to locate a right
ventricular active pace/sense electrode and indifferent pace/sense
electrode in relation to the right ventricle; an atrial lead
adapted to be advanced to the atria to locate atrial pace/sense
electrodes in relation to the atria; and a pulse generator
comprising: an atrial sense amplifier coupled to the atrial lead
for sensing spontaneous atrial depolarizations and providing atrial
sense event signals; an AV delay timer for timing out an AV delay
from the atrial sense event signals that are characterized as
non-refractory; a right ventricular sense amplifier coupled to the
right ventricular lead for sensing spontaneous cardiac
depolarizations in the right ventricle and providing right
ventricular sense event signals; a left ventricular sense amplifier
coupled to the right and left ventricular leads for sensing
spontaneous cardiac depolarizations in the left ventricle and
providing left ventricular sense event signals; an escape interval
timer for timing out a V-A escape interval establishing a pacing
rate from a selected one of the right and left ventricular sense
event signals occurring during the AV delay or the V-A escape
interval that is characterized as non-refractory; ventricular
pacing pulse generating means operable at the time-out of the AV
delay for delivering a first pacing pulse either as a right
ventricular pacing pulse across the active right ventricular
pace/sense electrode and a selected indifferent pacing electrode to
evoke a right ventricular depolarization or as a left ventricular
pacing pulse along a trans-ventricular pacing path between said
active left ventricular pace/sense electrode and said indifferent
right ventricular pace/sense electrode to the left ventricle to
evoke a left ventricular depolarization; and means responsive to
delivery of the first pacing pulse for restarting the timing out of
the V-A escape interval.
22. The pacemaker of claim 21, wherein: said escape interval timing
means further comprises means for timing out said pacing interval
from a right or left ventricular sense event signal; and said
pacing pulse generating means is operable upon provision of a left
ventricular sense event signal for selectively delivering one of a
right ventricular pacing pulse across said right ventricular active
and indifferent pace/sense electrodes and a left ventricular pacing
pulse across said left ventricular active pace/sense electrode and
said right ventricular indifferent pace/sense electrodes.
23. The pacemaker of claim 22, wherein said pulse generating means
further comprises triggered pacing delay timing means for timing
out a triggered pacing delay from the providing of a right
ventricular sense event signal or a left ventricular sense event
signal or the timing out of the pacing interval; and wherein: said
pulse generating means is operable at the time out of the triggered
pacing delay to selectively generate and deliver the left
ventricular pacing pulse across said left ventricular active
pace/sense electrode and said right ventricular indifferent
pace/sense electrodes when said right ventricular pacing pulse is
delivered across said right ventricular active and indifferent
pace/sense electrodes at the start of the triggered pacing delay
and to selectively generate and deliver the right ventricular
pacing pulse across said right ventricular active pace/sense and
indifferent electrodes when said left ventricular pacing pulse is
delivered across said left ventricular active pace/sense electrode
and said indifferent right ventricular pace/sense electrode at the
start of the triggered pacing delay.
Description
CROSS-REFERENCE TO RELATED APPLICATIONS
Reference is hereby made to the following, commonly assigned,
co-pending, U.S. Patent Applications which disclose common subject
matter: Ser. No. 09/067,729 filed Apr. 28, 1998 for MULTIPLE
CHANNEL, SEQUENTIAL, CARDIAC PACING SYSTEMS filed in the names of
C. Struble et al.; Serial No. 09/439,244 filed on event date
herewith for MULTI-SITE CARDIAC PACING SYSTEM HAVING CONDITIONAL
REFRACTORY PERIOD filed in the names of K. Kleckner et al.; Serial
No. 09/439,078 filed on even date herewith for MULTI-SITE CARDIAC
PACING SYSTEM HAVING TRIGGER PACE WINDOW in the names of C. Juran
et al.; Serial No. 09/439,569 filed on even date herewith for
CARDIAC PACING SYSTEM DELIVERING MULTI-SITE PACING IN A
PREDETERMINED SEQUENCE TRIGGERED BY A SENSE EVENT in the names of
C. Yerich et al.; Serial No. 09/439,568 filed on even date herewith
for RECHARGE CIRCUITRY FOR MULTI-SITE STIMULATION OF BODY TISSUE
filed in the names of B. Blow et al.; and Serial No. 09/439,243
filed on even date herewith for AV SYNCHRONOUS CARDIAC PACING
SYSTEM DELIVERING MULTI-SITE VENTRICULAR PACING TRIGGERED BY A
VENTRICULAR SENSE EVENT DURING THE AV DELAY in the names of C.
Yerich et al.
FIELD OF THE INVENTION
The present invention pertains to multi-site cardiac pacing systems
for pacing right and left heart chambers in inhibited and triggered
pacing modes employing combinations of right and left heart chamber
pace/sense electrodes for providing left heart chamber pacing and
sensing to facilitate placement of the left heart chamber
pace/sense electrode at a left heart chamber pace/sense site that
is difficult to access.
BACKGROUND OF THE INVENTION
In diseased hearts having conduction defects and in congestive
heart failure (CHF), cardiac depolarizations that naturally occur
in one upper or lower heart chamber are not conducted in a timely
fashion either within the heart chamber or to the other upper or
lower heart chamber. In patients suffering from CHF, the hearts may
become dilated, and the conduction and depolarization sequences of
the heart chambers may exhibit Intra-Atrial Conduction Defects
(IACD), Left Bundle Branch Block (LBBB), Right Bundle Branch Block
(RBBB), and Intra Ventricular Conduction Defects (IVCD). In such
cases, the right and left heart chambers do not contract in optimum
synchrony with each other, and cardiac output suffers due to the
conduction defects. In addition, spontaneous depolarizations of the
left atrium or left ventricle occur at ectopic foci in these left
heart chambers, and the natural activation sequence is grossly
disturbed. In such cases, cardiac output deteriorates because the
contractions of the right and left heart chambers are not
synchronized sufficiently to eject blood therefrom. Furthermore,
significant conduction disturbances between the right and left
atria can result in left atrial flutter or fibrillation.
It has been proposed that various conduction disturbances involving
both bradycardia and tachycardia of a heart chamber could benefit
from pacing pulses applied at multiple electrode sites positioned
in or about a single heart chamber or in the right and left heart
chambers in synchrony with a depolarization which has been sensed
at a minimum of at least one of the electrode sites. It is believed
that cardiac output can be significantly improved when left and
right chamber synchrony is restored, particularly in patients
suffering from dilated cardiomyopathy and CHF.
A number of proposals have been advanced for providing pacing
therapies to alleviate these conditions and restore synchronous
depolarization and contraction of a single heart chamber or right
and left, upper and lower, heart chambers as described in detail in
commonly assigned U.S. Pat. Nos. 5,403,356, 5,797,970 and 5,902,324
and in 5,720,768 and 5,792,203 all incorporated herein by
reference. The proposals appearing in U.S. Pat. Nos. 3,937,226,
4,088,140, 4,548,203, 4,458,677, 4,332,259 are summarized in U.S.
Pat. Nos. 4,928,688 and 5,674,259, all incorporated herein by
reference. The advantages of providing sensing at pace/sense
electrodes located in both the right and left heart chambers is
addressed in the '688 and '259 patents, as well as in U.S. Pat.
Nos. 4,354,497, 5,174,289, 5,267,560, 5,514,161, and 5,584,867,
also all incorporated herein by reference.
The medical literature also discloses a number of approaches of
providing bi-atrial and/or bi-ventricular pacing as set forth in:
Daubert et al., "Permanent Dual Atrium Pacing in Major Intra-atrial
Conduction Blocks: A Four Years Experience", PACE (Vol.16, Part II,
NASPE Abstract 141, p.885, April 1993); Daubert et al., "Permanent
Left Ventricular Pacing With Transvenous Leads Inserted Into The
Coronary Veins", PACE (Vol. 21, Part II, pp. 239-245, January
1998); Cazeau et al., "Four Chamber Pacing in Dilated
Cardiomyopathy", PACE (Vol. 17, Part II, pp. 1974-1979, November
1994); and Daubert et al., "Renewal of Permanent Left Atrial Pacing
via the Coronary Sinus", PACE (Vol. 15, Part II, NASPE Abstract
255, p. 572, April 1992), all incorporated herein by reference.
In the above-incorporated '768 patent, bipolar right heart chamber
leads and unipolar left heart chamber leads are employed. Sensing
of right heart depolarizations of the right heart chamber is
effected between right heart chamber active tip and indifferent
ring electrodes on the bipolar right heart lead. Sensing of the
left heart chamber depolarizations is effected between a single
left heart chamber active tip pace/sense electrode and the right
heart chamber active tip pace/sense electrode. Then, sensing is
switched to a unipolar mode to determine the true chamber of origin
of the sensed left heart depolarization. Right and left heart
chamber pacing to the other heart chamber is effected in a unipolar
manner, employing the IPG housing or canister as an indifferent IPG
"can" electrode.
In the above-incorporated '970 patent, bipolar left and right heart
chamber pacing leads are employed that are coupled to a single
sense amplifier and pacing output amplifier for sensing right and
left heart depolarizations and providing right and left heart
chamber pacing pulses. When sensing, the right and left heart
chamber active tip pace/sense electrodes are coupled together to
one input of the sense amplifier, and the right and left heart
chamber indifferent ring pace/sense electrodes are coupled together
to the other input of the sense amplifier. When pacing the right
heart chamber, the right and left heart chamber indifferent ring
pace/sense electrodes are coupled together, and a low energy pacing
pulse is delivered through the right heart chamber active tip
electrode. When pacing the left heart chamber, the right and left
heart chamber indifferent ring pace/sense electrodes are coupled
together, and a high energy pacing pulse is delivered through both
the right and left heart chamber active tip electrodes. The pacing
pulse energy is distributed along multiple pacing vectors, and in
fact both the right and left heart chambers are simultaneously
paced.
It is important that pacing energy be directed in a vector that
maximizes efficiency of capturing the heart. In addition, the
location of a left ventricular distal active pace/sense electrode
deep in a cardiac vein within the narrow vessel lumen necessitates
use of very small diameter unipolar lead bodies that do not allow
inclusion of an indifferent ring electrode and associated lead
conductor and insulation separating it from the lead conductor for
the active pace/sense electrode. Since the active pace/sense
electrode is separated from direct contact with the left
ventricular myocardium, the left ventricular pacing threshold is
likely to be higher than the right ventricular pacing threshold
requiring a higher energy left ventricular pacing pulse than right
ventricular pacing pulse. It is desirable to direct the left
ventricle pacing pulse in a left ventricular pacing vector that
traverses as great a bulk of the left ventricular myocardial mass
as possible. It is undesirable to dissipate that pacing pulse
energy in the right ventricle as is the case in approach disclosed
in the '970 patent or to direct it through a vector traversing only
a portion of the left ventricle to the remotely located indifferent
IPG can electrode as is the case in the unipolar pacing modes
disclosed in the above-incorporated '768 patent.
In the case of bi-atrial pacing systems, it is also desirable to
direct the left atrial pacing pulse in an efficient left atrial
pacing vector and to not dissipate pacing energy in body tissue or
in the right atrium.
SUMMARY OF THE INVENTION
The present invention is therefore directed to providing right and
left heart chamber pacing systems and methods of operation that
provide efficient pacing of the left heart chamber without
dissipating left heart chamber pacing energy.
In a bi-chamber pacing system, an IPG optionally having an
indifferent IPG can electrode is coupled to a small diameter,
unipolar, left heart chamber (LHC) endocardial lead and a bipolar
right heart chamber (RHC) endocardial lead. The LHC lead is
advanced through a venous pathway to locate the LHC active
pace/sense electrode at a desired LHC pace/sense site. The RHC lead
is advanced into the RHC chamber to locate RHC active and
indifferent pace/sense electrodes therein. Sensing of RHC
spontaneous cardiac depolarizations to provide a RHC sense event
signal and delivery of RHC pacing pulses is conducted across the
RHC active pace/sense electrode and one of the RHC or IPG
indifferent pace/sense electrodes. Sensing of LHC spontaneous
cardiac depolarizations to provide a LHC sense event signal is
conducted across the LHC active pace/sense electrode and one of the
RHC active or indifferent pace/sense electrodes or the IPG
indifferent can electrode. Delivery of LHC pacing pulses is
conducted across the LHC active pace/sense electrode and the RHC
indifferent pace/sense electrode, whereby the LHC pacing vector
traverses the mass of the LHC.
In a bi-ventricular pacing system, a small diameter, unipolar, left
ventricular, coronary sinus (LV CS) endocardial lead and a bipolar
right ventricular (RV) endocardial lead are preferably employed to
provide the LHC and RHC pace/sense electrodes. The LV CS lead is
advanced through the superior vena cava, the right atrium, the
ostium of the coronary sinus (CS), the CS, and into a coronary vein
descending from the CS to locate the LV active pace/sense electrode
at a desired LV pace/sense site. The RV lead is advanced into the
RV chamber to locate RV active and indifferent pace/sense
electrodes therein. Sensing of RV spontaneous cardiac
depolarizations to provide a RV sense event signal and delivery of
RV pacing pulses is conducted across the RV active pace/sense
electrode and one of the RV or IPG indifferent pace/sense
electrodes. Sensing of LV spontaneous cardiac depolarizations to
provide a LV sense event signal is conducted in a unipolar sensing
vector across the LV active pace/sense electrode and the IPG
indifferent pace/sense electrode or in a trans-ventricular sensing
vector across the LV active pace/sense electrode and one of the RV
active or indifferent pace/sense electrodes. Delivery of LV pacing
pulses is conducted across the LV active pace/sense electrode and
the RV indifferent pace/sense electrode and in a pacing vector that
encompasses the bulk of the LV.
In a bi-atrial pacing system, a unipolar, left atrial, coronary
sinus (LA CS) lead and a bipolar right atrial (RA) endocardial lead
are preferably employed to provide the LHC and RHC pace/sense
electrodes. Use of epicardial leads is of course an option. The
unipolar LA CS(or epicardial) lead locates an active LA pace/sense
electrode in relation to the LA, and the bipolar RA lead locates an
active RA pace/sense electrode and indifferent RA pace/sense
electrode in relation to the RA. Sensing of LA spontaneous cardiac
depolarizations to provide a LA sense event signal is conducted
across the LA active pace/sense electrode and one of the RA active
or indifferent pace/sense electrodes or the IPG indifferent
pace/sense electrodes. Delivery of LA pacing pulses is conducted
across the LA active pace/sense electrode and the RA indifferent
pace/sense electrode and in a pacing vector that encompasses the
bulk of the LA.
In the context of bi-atrial or bi-ventricular pacing systems and
methods, a number of triggered pacing modes are possible. In one
triggered pacing mode, a first pacing pulse can be delivered to the
RHC or LHC and a second pacing pulse delivered to the LHC or RHC,
respectively, after a triggered pacing delay. The two pacing pulses
can be delivered either upon a non-refractory sense event detected
in one of the heart chambers or upon timeout of a pacing escape
interval. Alternatively, following a non-refractory sense event in
the RHC or LHC, a single pacing pulse can be delivered to the LHC
or RHC, respectively after time-out of the triggered pacing delay
timed from the sense event. In still another triggered pacing mode,
a single pacing pulse can be delivered to the RHC or LHC where the
non-refractory sense event is detected.
The present invention is preferably implemented in systems for
providing atrial or ventricular bi-chamber pacing or AV synchronous
pacing systems for providing three or four chamber pacing.
The present invention is also preferably implemented into an
external or implantable pulse generator and lead system selectively
employing right and left heart, atrial and/or ventricular leads.
The preferred embodiment is implemented in an architecture that
allows wide programming flexibility for operating in AV synchronous
modes with right and left ventricular pacing or in atrial or
ventricular only modes for providing only right and left atrial or
ventricular pacing. The AV synchronous embodiments may be
implemented into an IPG or external pulse generator and lead system
providing right and left ventricular pacing and sensing and either
both right and left atrial pacing or just right or left atrial
pacing and sensing. Alternatively, the invention can be implemented
in IPGs or external pulse generators and lead systems having hard
wired connections and operating modes that are not as
programmable.
BRIEF DESCRIPTION OF THE DRAWINGS
These and other advantages and features of the present invention
will be more readily understood from the following detailed
description of the preferred embodiments thereof, when considered
in conjunction with the drawings, in which like reference numerals
indicate identical structures throughout the several views, and
wherein:
FIG. 1 is an illustration of transmission of the cardiac
depolarization waves through the heart in a normal electrical
activation sequence;
FIG. 2 is a schematic diagram depicting a three channel, atrial and
bi-ventricular, pacing system in which the present invention is
preferably implemented;
FIG. 3 is a simplified block diagrams of one embodiment of IPG
circuitry and associated leads employed in the system of FIG. 2 for
providing four pacing channels that are selectively programmed in
bi-atrial and/or bi-ventricular pacing modes;
FIG. 4 is a comprehensive flow-chart illustrating the operating
modes of the IPG circuitry of FIG. 3 in a variety of AV
synchronous, bi-ventricular pacing modes in accordance with one
embodiment of the invention;
FIG. 5 is a flow chart illustrating the steps of delivering
ventricular pacing pulses following time-out of an AV delay in FIG.
4;
FIGS. 6A-6B is a flow chart illustrating the steps of delivering
ventricular pacing pulses following a ventricular sense event
during the time-out of an AV delay or the V-A escape interval in
FIG. 4; and
FIG. 7 is a comprehensive flow-chart illustrating the operating
modes of the IPG circuitry of FIG. 3 in a variety of bi-atrial or
bi-ventricular pacing modes in accordance with a further embodiment
of the invention selectively employing steps of FIGS. 5 and 6
therein.
DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS
In the following detailed description, references are made to
illustrative embodiments for carrying out the invention. It is
understood that other embodiments may be utilized without departing
from the scope of the invention. For example, the invention is
disclosed in detail in FIGS. 2 and 3 in the context of an AV
sequential, bi-ventricular, pacing system operating in demand,
atrial tracking, and triggered pacing modes in accordance with
FIGS. 4 through 6A-6B for restoring synchrony in depolarizations
and contraction of left and right ventricles in synchronization
with atrial sensed and paced events for treating bradycardia in
those chambers. This embodiment of the invention is programmable to
operate as a three or four channel pacing system having an AV
synchronous operating mode for restoring upper and lower heart
chamber synchronization and right and left atrial and/or
ventricular chamber depolarization synchrony. But. it will be
realized that the invention can also be practiced in a
bi-ventricular or bi-atrial pacing system that can be dedicated to
such use or can be a programmable mode of the system of FIGS. 2 and
3 following the flow chart of FIG. 7. The invention can be
practiced in a two channel or four channel pacing system of the
type disclosed in the above-incorporated '324 patent as well.
It should be appreciated that the present invention may be utilized
particularly to treat patients suffering CHF and bradycardia. The
pacing system of the present invention may also may be incorporated
into an anti-tachyarrhythmia system including specific high rate
pacing and cardioversion shock therapies for providing staged
therapies to treat a diagnosed arrhythmia.
In FIG. 1, heart 10 includes the upper heart chambers, the right
atrium (RA) and left atrium (LA), and the lower heart chambers, the
right ventricle (RV) and left ventricle (LV) and the coronary sinus
(CS) extending from the opening in the right atrium laterally
around the atria to form the cardiac veins. FIG. 1 is an
illustration of transmission of the cardiac depolarization waves
through the RA, LA, RV and LV in a normal electrical activation
sequence at a normal heart rate with the conduction times exhibited
thereon in seconds. The cardiac cycle commences normally with the
generation of the depolarization impulse at the SA Node in the
right atrial wall and its transmission through the atrial
conduction pathways of Bachmann's Bundle and the Internodal Tracts
at the atrial level into the left atrial septum. The RA
depolarization wave reaches the Atrio-ventricular (AV) node and the
atrial septum within about 40 msec and reaches the furthest walls
of the RA and LA within about 70 msec, and the atria complete their
contraction as a result. The aggregate RA and LA depolarization
wave appears as the P-wave of the PQRST complex when sensed across
external ECG electrodes and displayed. The component of the atrial
depolarization wave passing between a pair of unipolar or bipolar
pace/sense electrodes, respectively, located on or adjacent the RA
or LA is also referred to as a sensed P-wave. Although the location
and spacing of the external ECG electrodes or implanted unipolar
atrial pace/sense electrodes has some influence, the normal P-wave
width does not exceed 80 msec in width as measured by a high
impedance sense amplifier coupled with such electrodes. A normal
near field P-wave sensed between closely spaced bipolar pace/sense
electrodes and located in or adjacent the RA or the LA has a width
of no more than 60 msec as measured by a high impedance sense
amplifier.
The depolarization impulse that reaches the AV Node is distributed
inferiorly down the bundle of His in the intraventricular septum
after a delay of about 120 msec. The depolarization wave reaches
the apical region of the heart about 20 msec later and then travels
superiorly though the Purkinje Fiber network over the remaining 40
msec. The aggregate RV and LV depolarization wave and the
subsequent T-wave accompanying repolarization of the depolarized
myocardium are referred to as the QRST portion of the PQRST cardiac
cycle complex when sensed across external ECG electrodes and
displayed. When the amplitude of the QRS ventricular depolarization
wave passing between a bipolar or unipolar pace/sense electrode
pair located on or adjacent the RV or LV exceeds a threshold
amplitude, it is detected as a sensed R-wave. Although the location
and spacing of the external ECG electrodes or implanted unipolar
ventricular pace/sense electrodes has some influence, the normal
R-wave width does not exceed 80 msec in width as measured by a high
impedance sense amplifier. A normal near field R-wave sensed
between closely spaced bipolar pace/sense electrodes and located in
or adjacent the RV or the LV has a width of no more than 60 msec as
measured by a high impedance sense amplifier.
The typical normal conduction ranges of sequential activation are
also described in the article by Durrer et al., entitled "Total
Excitation of the Isolated Human Heart", in CIRCULATION (Vol. XLI,
pp. 899-912, June 1970). This normal electrical activation sequence
becomes highly disrupted in patients suffering from advanced CHF
and exhibiting IACD, LBBB, RBBB, and/or IVCD. These conduction
defects exhibit great asynchrony between the RV and the LV due to
conduction disorders along the Bundle of His, the Right and Left
Bundle Branches or at the more distal Purkinje Terminals. Typical
intra-ventricular peak--peak asynchrony can range from 80 to 200
msec or longer. In RBBB and LBBB patients, the QRS complex is
widened far beyond the normal range to from >120 msec to 250
msec as measured on surface ECG. This increased width demonstrates
the lack of synchrony of the right and left ventricular
depolarizations and contractions.
In accordance with a first embodiment of the present invention, a
method and apparatus is provided to restore the depolarization
sequence of FIG. 1 and the synchrony between the right and left
ventricular heart chambers that contributes to adequate cardiac
output. This restoration is effected through providing optimally
timed cardiac pacing pulses to the right and left ventricles as
necessary and to account for the particular implantation sites of
the pace/sense electrodes in relation to each heart chamber while
maintaining AV synchrony. The present invention efficiently directs
the left heart chamber pacing pulses in a desirable pacing vector
that encompasses the bulk of the left heart chamber and facilitates
placement of the left heart chamber pace/sense electrodes at
desired pace/sense sites of the left heart chamber.
FIG. 2 is a schematic representation of an implanted, three channel
cardiac pacemaker of the above noted types for restoring AV
synchronous contractions of the atrial and ventricular chambers and
simultaneous or sequential pacing of the right and left ventricles.
The Implantable Pulse Generator IPG 14 is implanted subcutaneously
in a patient's body between the skin and the ribs. Three
endocardial leads 16, 32 and 52 connect the IPG 14 with the RA, the
RV and the LV, respectively. Each lead has at least one electrical
conductor and pace/sense electrode, and a remote indifferent can
electrode 20 is formed as part of the outer surface of the housing
of the IPG 14. As described further below, the pace/sense
electrodes and the remote indifferent can electrode 20 (IND_CAN
electrode) can be selectively employed to provide a number of
unipolar and bipolar pace/sense electrode combinations for pacing
and sensing functions. The depicted positions in or about the right
and left heart chambers are also merely exemplary. For instance,
any of the leads may be placed epicardially if desired, or there
may be other arrangements made. Moreover other leads and pace/sense
electrodes may be used instead of the depicted leads and pace/sense
electrodes that are adapted to be placed at electrode sites on or
in or relative to the RA, LA, RV and LV.
The depicted bipolar endocardial RA lead 16 is passed through a
vein into the RA chamber of the heart 10, and the distal end of the
RA lead 16 is attached to the RA wall by an attachment mechanism
17. The bipolar endocardial RA lead 16 is formed with an in-line
connector 13 fitting into a bipolar bore of IPG connector block 12
that is coupled to a pair of electrically insulated conductors
within lead body 15 and connected with distal tip RA pace/sense
electrode 19 and proximal ring RA pace/sense electrode 21. Delivery
of atrial pace pulses and sensing of atrial sense events is
effected between the distal tip RA pace/sense electrode 19 and
proximal ring RA pace/sense electrode 21, wherein the proximal ring
RA pace/sense electrode 21 functions as an indifferent electrode
(IND_RA). Alternatively, a unipolar endocardial RA lead could be
substituted for the depicted bipolar endocardial RA lead 16 and be
employed with the IND_CAN electrode 20. Or, one of the distal tip
RA pace/sense electrode 19 and proximal ring RA pace/sense
electrode 21 can be employed with the IND_CAN electrode 20 for
unipolar pacing and/or sensing.
Bipolar, endocardial RV lead 32 is passed through the vein and the
RA chamber of the heart 10 and into the RV where its distal ring
and tip RV pace/sense electrodes 38 and 40 are fixed in place in
the apex by a conventional distal attachment mechanism 41. The RV
lead 32 is formed with an in-line connector 34 fitting into a
bipolar bore of IPG connector block 12 that is coupled to a pair of
electrically insulated conductors within lead body 36 and connected
with distal tip RV pace/sense electrode 40 and proximal ring RV
pace/sense electrode 38, wherein the proximal ring RV pace/sense
electrode 38 functions as an indifferent electrode (IND_RV).
Alternatively, a unipolar endocardial RV lead could be substituted
for the depicted bipolar endocardial RV lead 32 and be employed
with the IND_CAN electrode 20. Or, one of the distal tip RV
pace/sense electrode 40 and proximal ring RV pace/sense electrode
38 can be employed with the IND_CAN electrode 20 for unipolar
pacing and/or sensing.
In this illustrated embodiment, a unipolar, endocardial LV CS lead
52 is passed through a vein and the RA chamber of the heart 10,
into the CS and then inferiorly in a branching vessel of the
cardiac vein 48 to extend the distal LV CS pace/sense electrode 50
alongside the LV chamber. The distal end of such LV CS leads is
advanced through the superior vena cava, the right atrium, the
ostium of the coronary sinus, the coronary sinus, and into a
coronary vein descending from the coronary sinus, such as the
cardiac vein. Typically, LV CS leads and LA CS leads do not employ
any fixation mechanism and instead rely on the close confinement
within these vessels to maintain the pace/sense electrode or
electrodes at a desired site. The LV CS lead 52 is formed with a
small diameter single conductor lead body 56 coupled at the
proximal end connector 54 fitting into a bore of IPG connector
block 12. A small diameter unipolar lead body 56 is selected in
order to lodge the distal LV CS pace/sense electrode 50 deeply in a
vein branching inferiorly from the great vein 48.
In accordance with the present invention, the distal, LV CS active
pace/sense electrode 50 is paired with the proximal ring RV
indifferent pace/sense electrode 38 for delivering LV pace pulses
across the bulk of the left ventricle and the intraventricular
septum. The distal LV CS active pace/sense electrode 50 is also
preferably paired with the distal tip RV active pace/sense
electrode 40 for sensing across the RV and LV as described further
below.
Moreover, in a four chamber embodiment, LV CS lead 52 could bear a
proximal LA CS pace/sense electrode positioned along the lead body
to lie in the larger diameter coronary sinus CS adjacent the LA. In
that case, the lead body 56 would encase two electrically insulated
lead conductors extending proximally from the more proximal LA CS
pace/sense electrode(s) and terminating in a bipolar connector 54.
The LV CS lead body would be smaller between the proximal LA CS
electrode and the distal LV CS active pace/sense electrode 50. In
that case, pacing of the RA would be accomplished along the pacing
vector between the active proximal LA CS active electrode and the
proximal ring RA indifferent pace/sense electrode 21.
FIG. 3 depicts bipolar RA lead 16, optional unipolar LA lead 62,
bipolar RV lead 32, and unipolar LV CS lead 52 coupled with an IPG
circuit 300 having programmable modes and parameters and a
telemetry transceiver of a DDDR type known in the pacing art. A
unipolar LA pace/sense electrode 64 is provided at the distal end
of the LA CS lead 62. The unipolar LA lead 62 may also be a CS lead
and may be formed as part of the LV CS lead 52 as described above.
The IPG circuit 300 is illustrated in a functional block diagram
divided generally into a microcomputer circuit 302 and a pacing
circuit 320. The pacing circuit 320 includes the digital
controller/timer circuit 330, the output amplifiers circuit 340,
and the sense amplifiers circuit 360, as well as a number of other
circuits and components described below.
Crystal oscillator circuit 338 provides the basic timing clock for
the pacing circuit 320, while battery 318 provides power.
Power-on-reset circuit 336 responds to initial connection of the
circuit to the battery for defining an initial operating condition
and similarly, resets the operative state of the device in response
to detection of a low battery condition. Reference mode circuit 326
generates stable voltage reference and currents for the analog
circuits within the pacing circuit 320, while analog to digital
converter ADC and multiplexer circuit 328 digitizes analog signals
and voltage to provide real time telemetry if a cardiac signals
from sense amplifiers 360, for uplink transmission via RF
transmitter and receiver circuit 332. Voltage reference and bias
circuit 326, ADC and multiplexer 328, power-on-reset circuit 336
and crystal oscillator circuit 338 may correspond to any of those
presently used in current marketed implantable cardiac
pacemakers.
If the IPG is programmed to a rate responsive mode, the signals
output by one or more physiologic sensor are employed as a rate
control parameter (RCP) to derive a physiologic escape interval.
For example, the escape interval is adjusted proportionally the
patient's activity level developed in the patient activity sensor
(PAS) circuit 322 in the depicted, exemplary IPG circuit 300. The
patient activity sensor 316 is coupled to the implantable pulse
generator housing 118 and may take the form of a piezoelectric
crystal transducer as is well known in the art and its output
signal is processed and used as the RCP. A timed interrupt, e.g.,
every two seconds, may be provided in order to allow the
microprocessor 304 to analyze the output of the activity circuit
PAS 322 and update the basic V-A (or A-A or V-V) escape interval
employed in the pacing cycle.
Data transmission to and from the external programmer is
accomplished by means of the telemetry antenna 334 and an
associated RF transmitter and receiver 332, which serves both to
demodulate received downlink telemetry and to transmit uplink
telemetry. Uplink telemetry capabilities will typically include the
ability to transmit stored digital information, e.g. operating
modes and parameters, EGM histograms, and other events, as well as
real time EGMs of atrial and/or ventricular electrical activity and
Marker Channel pulses indicating the occurrence of sensed and paced
depolarizations in the atrium and ventricle, as are well known in
the pacing art.
Microcomputer 302 contains a microprocessor 304 and associated
system clock 308 and on-processor RAM and ROM chips 310 and 312,
respectively. In addition, microcomputer circuit 302 includes a
separate RAM/ROM chip 314 to provide additional memory capacity.
Microprocessor 304 normally operates in a reduced power consumption
mode and is interrupt driven. Microprocessor 304 is awakened in
response to defined interrupt events, which may include A-PACE,
RV-PACE, LV-PACE signals generated by timers in digital
timer/controller circuit 330 and A-EVENT, RV-EVENT, and LV-EVENT
signals generated by sense amplifiers circuit 360, among others.
The specific values of the intervals and delays timed out by
digital controller/timer circuit 330 are controlled by the
microcomputer circuit 302 by means of data and control bus 306 from
programmed-in parameter values and operating modes.
In one embodiment of the invention, microprocessor 304 is a custom
microprocessor adapted to fetch and execute instructions stored in
RAM/ROM unit 314 in a conventional manner. It is contemplated,
however, that other implementations may be suitable to practice the
present invention. For example, an off-the-shelf, commercially
available microprocessor or microcontroller, or custom
application-specific, hardwired logic, or state-machine type
circuit may perform the functions of microprocessor 304.
Digital controller/timer circuit 330 operates under the general
control of the microcomputer 302 to control timing and other
functions within the pacing circuit 320 and includes a set of
timing and associated logic circuits of which certain ones
pertinent to the present invention are depicted. The depicted
timing circuits include discharge/recharge timers 364, V-V delay
timer 366, an intrinsic interval timer 368 for timing elapsed
V-EVENT to V-EVENT intervals or V-EVENT to A-EVENT intervals,
escape interval timers 370 for timing A-A, V-A, and/or V-V pacing
escape intervals, an AV delay interval timer 372 for timing an AV
delays from a preceding A-EVENT (SAV) or A-PACE (PAV), a
post-ventricular timer 374 for timing post-ventricular time
periods, and an upper rate interval (URI) timer 376. RHC pace
trigger and sense events are typically used for starting and
resetting these intervals and periods. However, it would be
possible to allow the physician to select and program LHC pace
trigger and sense events for these timing purposes.
Microcomputer 302 controls the operational functions of digital
controller/timer circuit 330, specifying which timing intervals are
employed, and setting at least the programmed-in base timing
intervals, via data and control bus 306. Digital controller/timer
circuit 330 starts and times out these intervals and delays for
controlling operation of the atrial and ventricular sense
amplifiers in sense amplifiers circuit 360 and the atrial and
ventricular pace pulse generators in output amplifiers circuit
340.
The post-event timers 374 time out the post-ventricular time
periods following an RV-EVENT or LV-EVENT or a RV-PACE or LV-PACE
and post-atrial time periods following an A-EVENT or A-PACE. The
durations of the post-event time periods may also be selected as
programmable parameters stored in the microcomputer 302. The
post-ventricular time periods include the PVARP, a post-atrial
ventricular blanking period (PAVBP), a ventricular blanking period
(VBP), a ventricular refractory period (VRP), and a conditional
ventricular refractory period (CVRP). The post-atrial time periods
include an atrial refractory period (ARP) during which an A-EVENT
is ignored for the purpose of resetting the AV delay, and an atrial
blanking period (ABP) during which atrial sensing is disabled.
These post-atrial time periods time out concurrently with the
time-out of the SAV or PAV delay started by an A-EVENT or an
A-PACE.
It should be noted that the starting of the post-atrial time
periods and the AV delays can be commenced substantially
simultaneously with the start or end of the A-EVENT or A-PACE.
Similarly, the starting of the post-ventricular time periods and
the V-A escape interval can be commenced substantially
simultaneously with the start or end of the V-EVENT or V-PACE.
The microprocessor 304 also optionally calculates AV delays,
post-ventricular time periods, and post-atrial time periods which
vary with the sensor based escape interval established in response
to the RCP(s) and/or with the intrinsic atrial rate. The variable
AV delays are usually derived as an offset of a maximum AV delay
set for the pacing lower rate (i.e., the longest escape
interval).
The output amplifiers circuit 340 contains a RA pace pulse
generator, a LA pace pulse generator, a RV pace pulse generator and
a LV pace pulse generator or corresponding to any of those
presently employed in commercially marketed cardiac pacemakers
providing atrial and ventricular pacing. In order to trigger
generation of an RV-PACE or LV-PACE pulse, digital controller/timer
circuit 330 generates a RV-TRIG or LV-TRIG signal at the end of an
AV delay provided by AV delay interval timer 372. Similarly, in
order to trigger a right or left atrial pacing or RA-PACE pulse or
LA-PACE pulse, digital controller/timer circuit 330 generates an
RA-TRIG or LA-TRIG signal at the end of the V-A escape interval
timed by escape interval timers 370.
Typically, in pacing systems of the type illustrated in FIGS. 2 and
3, the electrodes designated above as "pace/sense" electrodes are
used for both pacing and sensing functions. In accordance with one
aspect of the present invention, these "pace/sense" electrodes can
be selected to be used exclusively as pace or sense electrodes or
to be used in common as pace/sense electrodes in programmed
combinations for sensing cardiac signals and delivering pacing
pulses along pacing and sensing vectors. Separate or shared
indifferent pace and sense electrodes can also be designated in
pacing and sensing functions. For convenience, the following
description separately designates pace and sense electrode pairs
where a distinction is appropriate.
The output amplifiers circuit 340 includes switching circuits for
coupling selected pace electrode pairs from among the lead
conductors and the IND_CAN electrode 20 to the RA pace pulse
generator, LA pace pulse generator, RV pace pulse generator and LV
pace pulse generator. Pace/sense electrode pair selection and
control circuit 350 selects lead conductors and associated pace
electrode pairs to be coupled with the atrial and ventricular
output amplifiers within output amplifiers circuit 340 for
accomplishing RA, LA, RV and LV pacing as described below.
The sense amplifiers circuit 360 contains sense amplifiers
corresponding to any of those presently employed in commercially
marketed cardiac pacemakers for atrial and ventricular pacing and
sensing. As noted in the above-referenced, commonly assigned, '324
patent, it has been common in the prior art to use very high
impedance P-wave and R-wave sense amplifiers to amplify the voltage
difference signal which is generated across the sense electrode
pairs by the passage of a cardiac depolarization. The high
impedance sense amplifiers use high gain to amplify the low
amplitude signals and rely on pass band filters, time domain
filtering and amplitude threshold comparison to discriminate a
P-wave or R-wave from background electrical noise. Digital
controller/timer circuit 330 controls sensitivity settings of the
atrial and ventricular sense amplifiers 360.
The sense amplifiers are uncoupled from the sense electrodes during
the blanking periods before, during, and after delivery of a pacing
pulse to any of the pace electrodes of the pacing system to avoid
saturation of the sense amplifiers. The sense amplifiers circuit
360 includes blanking circuits for uncoupling the selected pairs of
the lead conductors and the IND_CAN electrode 20 from the inputs of
the RA sense amplifier, LA sense amplifier, RV sense amplifier and
LV sense amplifier during the ABP, PVABP and VBP. The sense
amplifiers circuit 360 also includes switching circuits for
coupling selected sense electrode lead conductors and the IND_CAN
electrode 20 to the RA sense amplifier, LA sense amplifier, RV
sense amplifier and LV sense amplifier. Again, sense electrode
selection and control circuit 350 selects conductors and associated
sense electrode pairs to be coupled with the atrial and ventricular
sense amplifiers within the output amplifiers circuit 340 and sense
amplifiers circuit 360 for accomplishing RA, LA, RV and LV sensing
along desired unipolar and bipolar sensing vectors.
Right atrial depolarizations or P-waves in the RA-SENSE signal that
are sensed by the RA sense amplifier result in a RA-EVENT signal
that is communicated to the digital controller/timer circuit 330.
Similarly, left atrial depolarizations or P-waves in the LA-SENSE
signal that are sensed by the LA sense amplifier result in a
LA-EVENT signal that is communicated to the digital
controller/timer circuit 330. Ventricular depolarizations or
R-waves in the RV-SENSE signal are sensed by a ventricular sense
amplifier result in an RV-EVENT signal that is communicated to the
digital controller/timer circuit 330. Similarly, ventricular
depolarizations or R-waves in the LV-SENSE signal are sensed by a
ventricular sense amplifier result in an LV-EVENT signal that is
communicated to the digital controller/timer circuit 330. The
RV-EVENT, LV-EVENT, and RA-EVENT, LA-SENSE signals may be
refractory or non-refractory, and can inadvertently be triggered by
electrical noise signals or aberrantly conducted depolarization
waves rather than true R-waves or P-waves.
In accordance with the present invention, sensing of RHC (RA and/or
RV) spontaneous cardiac depolarizations to provide a RHC sense
event signal(RA-SENSE and/or RV-SENSE) and delivery of RHC pacing
pulses (RA-PACE and/or RV-PACE) is conducted across the RHC active
pace/sense electrode (9 and/or 40) and one of the RHC indifferent
ring, pace/sense electrodes (21 and/or 38) or IPG indifferent
pace/sense electrodes (IND_CAN 20). Sensing of LHC spontaneous
cardiac depolarizations (LA-SENSE and/or LV-SENSE) to provide a LHC
sense event signal (LA-EVENT and/or LV-EVENT) is conducted in a
trans-ventricular sensing vector across the LHC active pace/sense
electrode and one of the RHC active or indifferent pace/sense
electrodes or the IPG indifferent can electrode. Delivery of LHC
pacing pulses (LA-PACE and/or LV-PACE) is conducted across the LHC
active pace/sense electrode (64 and/or 50) and the RHC indifferent
ring pace/sense electrode (21 and/or 38), whereby the LHC pacing
vector traverses the mass of the LHC.
Advantageously, the pacemaker of FIG. 3 could be simplified by
providing only a single atrial sense amplifier coupled to a
trans-atrial sense electrode pair comprising the active CS LA and
the active RA pace/sense electrodes 64 and 19. Then, only a single
A-EVENT would be provided and employed, and it may reflect either a
RA-SENSE or a LA-SENSE. Similarly, the pacemaker could be
simplified by providing only a single ventricular sense amplifier
coupled to the active CS LV and the active distal tip RV pace/sense
electrodes 50 and 40 to provide a single trans-ventricular sensing
vector. Then, only a single V-EVENT would be provided and
employed.
To simplify the description of FIGS. 4 through 6A-6B, it will be
assumed that the following references to an "A-EVENT" and "A-PACE"
will be the RA-EVENT and RA-PACE, respectively, if there is no LA
pacing or sensing provided or programmed on, or will be a
programmed one of the RA-EVENT or LA-EVENT and RA-PACE or LA-PACE,
respectively. The A-EVENT could also be the output sense event
signal of the single atrial sense amplifier coupled to active
pace/sense electrodes 19 and 64.
The general operation of IPG circuit 300 is depicted in the flow
chart of FIG. 4. The AV delay is started in step S100 when a P-wave
outside of refractory is sensed across the selected atrial sense
electrode pair during the V-A escape interval (an A-EVENT) as
determined in step S134 or an A-PACE pulse is delivered to the
selected atrial pace electrode pair in step S118. The AV delay can
be a PAV or SAV delay, depending upon whether it is started on an
A-PACE or an A-EVENT, respectively, and is timed out by the SAV/PAV
delay timer 372. The SAV or PAV delay is terminated upon a
non-refractory RV-EVENT or LV-EVENT output by a ventricular sense
amplifier prior to its time-out.
The post-event timers 374 are started to time out the
post-ventricular time periods and the TRIG_PACE window, and the V-A
escape interval timer 370 is started to time out the V-A escape
interval in step S104 if the SAV or PAV delay times out in step
S102 without the detection of a non-refractory RV-EVENT or
LV-EVENT. The TRIG_PACE window inhibits triggered pacing modes in
response to a sense event occurring too early in the escape
interval and is described in greater detail in the above-referenced
application Ser. No. 09/439,078.
Either a programmed one or both of the RV-PACE and LV-PACE pulses
are delivered in step S106 (as shown in FIG. 5) to selected RV and
LV pace electrode pairs, and the V-A escape interval timer is timed
out in step S116. When both of the RV-PACE and LV-PACE pulses are
delivered, the first is referred to as V-PACE1, the second is
referred to as V-PACE2, and they are separated by a VP-VP delay. As
described in greater detail below in reference to FIGS. 6A-6B, if a
bi-ventricular pacing mode is programmed in step S106, it can be
selectively programmed in a left-to-right or right-to-left
ventricle pacing sequence wherein the first and second delivered
ventricular pacing pulses are separated by separately programmed
VP-VP delays. The VP-VP delays are preferably programmable between
nearly 0 msec (say for example 4 msecs) and about 80 msec.
Returning to step S102, the AV delay is terminated if an RV-EVENT
or LV-EVENT (collectively, a V-EVENT) is generated by the RV sense
amplifier or the LV sense amplifier in step S108. The time-out of
the V-A escape interval and the post-ventricular time periods are
started in step S110 in response to the V-EVENT. In step S112, it
is determined whether a ventricular triggered pacing mode is
programmed to be operative during the AV delay. If one is
programmed on, then it is undertaken and completed in step S114
(FIGS. 6A-6B). If a ventricular triggered pacing mode is not
programmed on as determined in step S112, then no ventricular
pacing is triggered by a sensed non-refractory V-EVENT terminating
the AV delay. The time-out of the TRIG_PACE window is commenced in
step S113 simultaneously with the time-out of the V-A escape
interval and post-event time periods in step S110. The time-out of
the TRIG_PACE window is commenced in step S113 simultaneously with
the time-out of the V-A escape interval and post-event time periods
in step S110.
If the V-A atrial escape interval is timed out by timer 370 in step
S116 without a non-refractory A-EVENT being sensed across the
selected pair of atrial sense electrodes, then the A-PACE pulse is
delivered across the selected RA pace electrode pair in step S118,
the AV delay is set to PAV in step S120, and the AV delay is
commenced by AV delay timer 372.
If a non-refractory A-EVENT is generated as determined in steps
S122 and S134, then the V-A escape interval is terminated. The ABP
and ARP are commenced by post-event timers 374 in step S134, the AV
delay is set to the SAV in step S138, and the SAV delay is started
in step S100 and timed out by SAV/PAV delay timer 372.
Assuming that the normal activation sequence is sought to be
restored, a programmed SAV and PAV delay corresponding to a normal
AV conduction time from the AV node to the bundle of His are used
or a calculated SAV and PAV delay is calculated in relation to the
prevailing sensor rate or sensed intrinsic heart rate and are used
by SAV/PAV delay timer 372.
If an RV-EVENT or LV-EVENT or a collective V-EVENT sensed across
the RV tip sense electrode and the LV sense electrode (for
simplicity, all referred to as a V-EVENT) is detected in step S123
during the time-out of the V-A escape interval, then, it is
determined if it is a non-refractory V-EVENT or a refractory
V-EVENT in step S124. If an RV-EVENT or LV-EVENT (collectively a
V-EVENT) is sensed during the time-out of the V-A escape interval
in step S123, then, it is determined if it is a non-refractory
V-EVENT or a refractory V-EVENT in step S124. If the V-EVENT is
determined to be a refractory V-EVENT in step S124, then it is
employed in the CVRP processing step S126 which is described in
detail in the above-referenced application Ser. No. 09/439,244. If
the V-EVENT is determined to be a non-refractory V-EVENT in step
S124, then the V-A escape interval is restarted, and the
post-ventricular time periods are restarted in step S128.
In step S130, it is determined whether a triggered pacing mode is
programmed to be operative during the V-A escape interval. If one
is programmed on, then it is undertaken and completed in step S132
(FIGS. 6A-6B). If triggered pacing is not programmed on as
determined in step S130, then no ventricular pacing is triggered by
the sensed non-refractory V-EVENT during the V-A escape interval.
The time-out of the TRIG_PACE window is commenced in step S131
simultaneously with the time-out of the V-A escape interval and
post-event time periods in step S128.
FIG. 5 depicts the step S106 in greater detail, and FIGS. 6A-6B
depict the steps S114 and S132 in greater detail. As described in
greater detail below, if a VP-VP pacing mode is programmed on in
step S106, it can be selectively programmed in a left-to-right or
right-to-left ventricle sequence, wherein the first and second
delivered ventricular pacing pulses (V-PACE1 and V-PACE2) are
separated by separately programmed VP-VP delays. If a
bi-ventricular triggered pacing mode is programmed on in either or
both of steps S114 and S132, it can be selectively programmed to
immediately pace the ventricle from which the V-EVENT is sensed or
a fixed or programmed ventricle regardless of where the V-EVENT is
sensed with a V-PACE1. Then, the V-PACE2 is generated to
synchronously pace the other ventricle after a programmed VS/VP-VP
delay. Or, the triggered pacing mode can be selectively programmed
in either or both of steps S114 and 132 to only synchronously pace
the other ventricle than the ventricle from which the V-EVENT is
sensed with V-PACE2 after separately programmable VS-VP delays,
depending on the right-to-left or left-to-right sequence. All of
these VP-VP, VS/VP-VP, and VS-VP delays are preferably programmable
between nearly 0 msec and about 80 msec. As a practical matter, the
minimum VS/VP-VP, and VP-VP delays may be set to one half the
system clock cycle in order to avoid simultaneous delivery of
RV-PACE and LV-PACE pulses. The pacing pulse width is typically
programmable between about 0.5 msec and 2.0 msec, and the pacing
pulse amplitude is typically programmable between 0.5 and 7.5
volts. The system clock provides a full clock cycle of about 8.0
msec. Therefore, the minimum VP-VP delay is set at a half clock
cycle or about 4.0 msec.
It is desired to be able to deliver RV-PACE and LV-PACE pulses that
differ from one another in pulse width and amplitude in order to
make certain that the delivered energy is sufficient to capture the
heart chamber without being unduly wasteful of energy. But, if
differing amplitude and pulse width RV-PACE and LV-PACE pulses are
simultaneously delivered to the right and left ventricles, then DC
current pathways can develop between the active electrodes that can
cause aberrant conduction pathways in the heart and can lead to
oxidation or other deterioration of the pace/sense electrodes.
In addition, when a pacing system is implanted, the physician
undertakes a work-up of the patient to determine the pacing energy
and sensing thresholds that are sufficient to capture the heart and
to distinguish true P-waves and R-waves from muscle artifacts and
ambient electrical noise. If LV-PACE and RV-PACE pulses are
delivered simultaneously, there may be a current contribution from
the highest voltage active electrode delivering the highest voltage
pulse to the lower voltage active electrode delivering the lower
voltage pulse. The contribution may be sufficient to lower the
pacing threshold at the lowest voltage active electrode. Then, at a
later time, the programmed mode may be changed by eliminating or
lowering the voltage of the highest voltage pacing pulse, and
capture may be lost at the lowest voltage active pacing
electrode.
As shown in FIG. 5, the IPG circuit 300 of FIG. 3 can be programmed
to either only deliver a single RV-PACE or LV-PACE (V-PACE1) or the
pair of RV-PACE and LV-PACE pulses (V-PACE1 and V-PACE2) separated
by the VP-VP delay timed out by V-V delay timer 366. If delivery of
only a single RV-PACE or LV-PACE is programmed as determined in
step S200, then it is delivered in step S202.
In accordance with the present invention, the LV-PACE pulse is
delivered across the active LV pace electrode 50 and the
indifferent ring RV (IND_RV) pace electrode 38 in a
trans-ventricular pacing path 60 (shown schematically in FIG. 2)
encompassing the bulk of the LV and intraventricular septum
separating the pace/sense electrodes. Although the active RV pace
electrode 40 could be programmed to be paired as the indifferent
electrode with the active LV pace electrode 50 it is generally not
desirable to do so since both are of relatively small surface area,
and it is usually desirable to provide a relatively large
indifferent electrode surface area to function as an anode.
If VP-VP pacing is programmed on in step S200, then V-PACE1 is
delivered in step S204 in the programmed RV-LV or LV-RV sequence.
Again, the RV-PACE pulse is typically delivered across the active
RV tip electrode 40 and one of the available indifferent electrodes
that is programmed and selected through the pace/sense electrode
selection and control 350 depending upon which are present in the
pacing system and the RV pacing vector that is desired as set forth
above. And, the LV-PACE pulse is delivered across the active LV
pace electrode 50 and the IND_RV pace electrode 38 in the
trans-ventricular pacing path 60. The V-PACE1 pacing pulse is
delivered at a programmed pulse energy dictated by the programmed
voltage and pulse width.
The V-V delay timer 366 is loaded with the programmed VP-VP delay
and starts to time out in step S206. If the RV-PACE pulse is
V-PACE1, then a programmed VP-VP delay is timed in V-V delay timer
366. The LV-PACE pulse is delivered as V-PACE2 in the LV pacing
path 60 between the active LV pace electrode 50 and IND_RV pace
electrode 38 in step S210 after time-out of the programmed VP-VP
delay in step S208. Conversely, if the LV-PACE pulse is the first
to be delivered (V-PACE1) in the pacing path 60, then a programmed
VP-VP delay is timed in V-V delay timer 366. The RV-PACE pulse is
then delivered as V-PACE2 typically across the active RV pace
electrode 40 and the programmed indifferent electrode in step S210
after time-out of the programmed VP-VP delay in step S208.
FIGS. 6A-6B is a flow chart illustrating the steps S112 and S132 of
FIG. 4 for delivering ventricular pacing pulses triggered by a
ventricular sense event in step S108 during the time-out of an AV
delay or in step S124 during time-out of the V-A escape interval.
As noted above, the sensing of R-waves in the RV and LV can be
accomplished employing several RV-SENSE and LV-SENSE sensing axes
or vectors. A bipolar RV-SENSE vector (RV sense electrodes 38 and
40), a unipolar RV-SENSE vector (RV tip sense electrode 40 and
IND_CAN electrode 20), and a unipolar LV-SENSE vector (LV sense
electrode 50 and IND_CAN electrode 20), and a trans-ventricular,
combined RV-SENSE and LV-SENSE vector (RV tip sense electrode 40
and LV sense electrode 50) can be programmed. The selection of the
sensing vectors would depend upon heart condition and the selection
of the pacing pulse pathways.
The IPG circuit 300 can be separately programmed in one of three
triggered pacing modes designated VS/VP, VS/VP-VP or VS-VP
triggered modes for each of steps S114 and S132. In the VS/VP
triggered pacing mode, a V-PACE1 is delivered without delay upon a
RV-EVENT or LV-EVENT to the RV or LV pacing pathway, respectively.
In the VS/VP-VP triggered pacing mode, the V-PACE1 is delivered
without delay upon a RV-EVENT or LV-EVENT to the selected RV or LV
pacing electrode pair, respectively, and a V-PACE2 is delivered to
the other of the selected LV or RV pacing electrode pair after the
VSNP-VP delay times out. In the VS-VP pacing mode, a RV-EVENT or
the LV-EVENT starts time-out of a VS-VP delay, and a single pacing
pulse (designated V-PACE2) is delivered to the selected LV or the
RV pace electrode pair, respectively, when the VS-VP delay times
out.
The TRIG_PACE time window started by a prior V-EVENT or V-PACE must
have timed out in step S300 prior to delivery of any triggered
ventricular pacing pulses. If it has not timed out, then triggered
pacing cannot be delivered in response to a sensed V-EVENT. If the
TRIG_PACE window has timed out, it is then restarted in step S302,
and the programmed triggered pacing modes are checked in steps S304
and S316.
When IPG circuit 300 is programmed in the VS/VP-VP triggered mode
as determined in step S304, the RV-EVENT or LV-EVENT triggers the
immediate delivery of a respective RV-PACE or a LV-PACE or a
programmed one of the RV-PACE or a LV-PACE across the programmed
bipolar or unipolar RV and LV pace electrode pair, respectively, in
step S306 as V-PACE1. Under certain circumstances, it is desirable
to always deliver V-PACE1 to a designated RV or LV pace electrode
pair, regardless of whether a RV-EVENT and LV-EVENT is sensed.
Then, a VS/VP-VP delay is started in step S308 and timed out in
step S310. The VS/VP-VP delay is specified as a VP-VP delay when
the RV-EVENT is sensed and the RV-PACE is V-PACE1 and the LV-PACE
is V-PACE2. The VS/VP-VP delay is specified as a VP-VP delay when
the LV-EVENT is sensed and the LV-PACE is V-PACEI and the RV-PACE
is V-PACE2. The LV-PACE or RV-PACE pulse is delivered at the
programmed amplitude and pulse width across the programmed LV or RV
pace electrode pair in step S210.
In step S314, it is determined whether the VS-VP triggered pacing
mode or the VS/VP triggered pacing mode is programmed. When the IPG
circuit 300 is programmed to a single heart chamber VS/VP triggered
pacing mode, the RV-EVENT or LV-EVENT triggers the immediate
delivery of an RV-PACE or an LV-PACE across the programmed bipolar
or unipolar RV or LV pace electrode pair, respectively, in step
S316.
When the IPG circuit 300 is programmed to the VS-VP triggered
pacing mode, an LV-EVENT as determined in step S318 loads the
appropriate VS-VP delay in V-V delay timer 366 in step S320 and
starts the VS-VP delay time-out in step S322. The RV-PACE is
delivered at its time-out in step S322 (also designated V-PACE2).
If an RV-EVENT is determined in step S318, then the appropriate
VS-VP delay in V-V delay timer 366 in step S326 and the VS-VP delay
is timed out in step S328. The LV-PACE (also designated V-PACE2) is
delivered at time-out of the VS-VP delay in step S330.
The V-A escape interval is timed out in step S116 following the
completion of the ventricular pacing mode of FIGS. 6A-6B for steps
S114 and S132. If the V-A escape interval times out, then an RA
pace pulse is typically first delivered across the RA pace
electrodes 17 and 19 in step S118, and the AV delay timer is
restarted in step S100.
In all of steps S306, S312, S316, S324 and S330, the LV-PACE pulse
is delivered as V-PACE2 in the LV pacing path 60 between the active
LV pace electrode 50 and IND_RV pace electrode 38.
The present invention may also be advantageously implemented in
many of the bi-chamber pacing systems described above, e.g. those
described in the above-incorporated '324 patent. There is for
example no reason it could not be used in conjunction with an
Implantable Cardio-Defibrillator (ICD) assuming the ICD also
provides the inventive features. For example, FIG. 7 is a
comprehensive flow-chart illustrating the operating modes of the
IPG circuit 300 of FIG. 3 in a variety of bi-atrial or
bi-ventricular pacing modes in accordance with a further embodiment
of the invention selectively employing steps of FIGS. 4 through
6A-6B therein. It will be assumed, for example, that the AV
synchronous pacing DDD(R) mode is changed to an atrial or
ventricular demand, and triggered pacing mode. When FIGS. 4 through
6A-6B are incorporated into steps of FIG. 7 as described below, it
will be understood that references to the ventricles (V) in those
flow chart steps are appropriate to the bi-ventricular pacing
system and method. However, references to the atria (A) can be
substituted for the references to the ventricles (V) in those flow
chart steps for an understanding of a bi-atrial pacing system and
method in accordance with the present invention, where the LA-PACE
pulse is delivered across a LA pace electrode pair comprising the
active LA pace electrode 64 and the indifferent ring RA (IND_RA)
pace electrode 21.
In step S400, the pacing escape interval started in step S418 from
a prior R-SENSE or L-SENSE or previously delivered R-PACE or L-PACE
(PACE1) is timing out. If the escape interval times out, then the
TRIG-PACE window and the post-event time periods, including a
conditional refractory period (CRP), the URI and the refractory
period (RP) are commenced and timed out in step S402. At the same
time, at least a PACE1 pacing pulse is delivered to one of the RHC
or LHC in step S404, and the escape interval is restarted in step
S418. Step S404 is completed in accordance with the steps of FIG. 5
as described above to either deliver a PACE1 to the selected RHC or
LHC pace electrodes or to deliver both PACE1 and PACE2 to both the
selected RHC and LHC pace electrodes in a programmed right-to-left
or left-to right sequence separated by a programmed P-P delay.
A sense EVENT that is output by any of the RHC or LHC or the
trans-chamber sense amplifier during the escape interval in step
S402 is characterized as a refractory or non-refractory sense EVENT
in step S406. If it is a refractory sense EVENT, then the CRP
processing steps are followed as described in the above-referenced
09/439,244 application to determine if it falls within or follows
the time-out of the CRP and by how much the post-event time periods
are to be continued or extended. In this case, the post-event time
periods do not include a PVARP or PVABP, and only include a BP, RP,
and URI plus the CRP. The refractory sense EVENT does not trigger
delivery of any V-PACE pulses.
If a non-refractory sense EVENT occurs, then the CRP, the URI and
the RP are commenced and timed out in step S412. At the same time,
it is determined whether a triggered pacing mode is programmed on
in step S414. If triggered pacing is off, then the escape interval
is restarted in step S418 timed with the non-refractory sense EVENT
detected in step S408, and the steps of FIGS. 6A and 6B are
followed in step S416.
Triggered pacing proceeds if programmed on in step S416 and if the
non-refractory R-EVENT or L-EVENT falls outside the TRIG_PACE
window as determined In steps S300 and S302 of FIG. 6A. If
triggered pacing is programmed on, then it can be programmed to
deliver PACE 1 or PACE2 alone or both PACE1 and PACE2 in the manner
prescribed in the remaining steps of FIGS. 6A and 6B. The triggered
pacing modes can include delivering PACE1 alone to the RHC or LHC
where the sense EVENT was provided or to a programmed one of the
right or left heart chamber, regardless of where the depolarization
was sensed per step S316.
Or, PACE 1 and PACE2, separated by the programmed or fixed
PACE1-PACE2 trigger delay, can be delivered per steps S306-S312 in
a programmed sequence. The programmed sequence can comprise
delivering PACE1 to the heart chamber where the EVENT was provided
or to a programmed one of the RHC or LHC, regardless of where the
depolarization was sensed, and then delivering PACE 2 to the other
heart chamber at the time-out of the PACE1-PACE2 trigger delay.
Finally, delivery of PACE2 only can be programmed on, as determined
in step S314. In that case, steps S314-S330 are followed as
described above to deliver PACE2 to the other heart chamber than
the heart chamber where the EVENT was provided by the sense
amplifier coupled to it after time-out of a SENSE-PACE2 trigger
delay.
The preceding specific embodiments are illustrative of the practice
of the invention. It is to be understood, therefore, that other
expedients known to those of skill in the art or disclosed herein
may be employed.
It will be understood that certain of the above-described
structures, functions and operations of the pacing systems of the
preferred embodiments are not necessary to practice the present
invention and are included in the description simply for
completeness of an exemplary embodiment or embodiments. It will
also be understood that there may be other structures, functions
and operations ancillary to the typical operation of such pacing
systems that are not disclosed and are not necessary to the
practice of the present invention. In addition, it will be
understood that specifically described structures, functions and
operations set forth in the above-listed, commonly assigned and
co-pending patent applications can be practiced in conjunction with
the present invention, but they are not essential to its
practice.
In the following claims, means-plus-function clauses are intended
to cover the structures described herein as performing the recited
function and not only structural equivalents but also equivalent
structures.
It is therefore to be understood, that within the scope of the
appended claims, the invention may be practiced otherwise than as
specifically described without actually departing from the spirit
and scope of the present invention.
* * * * *